General relation of temperature characteristics for long-period fiber grating (LPG) is obtained from deduction by using mode coupling theory. Thermal-optics coefficient differences of guiding mode in fiber and coupled different cladding mode are determined through measurement of temperature characteristics for LPG with period of 400～600 μm. The relations of temperature sensitivity with grating periods and coupled cladding mode orders are summarized combining the formula of temperature characteristics for LPG. The method of improving temperature stability for LPG is presented on the basis of theory along with experiments.

A wavelength domain simulation method for wavelength-division-multiplexed (WDM) all optical network is presented. The optical spectra of WDM channels through 3 cascaded optical add-drop multiplexers (OADM′s) are simulated, and compared with experimental results. It is shown that after the WDM signals propagate through 50 OADM′s, the optical signal noise ratio (SNR) is above the acceptable level necessary to achieve a bit-error-rate (BER) lower than 10-9at 10 Gb/s. These simulations indicate that a future national or regional scale transparent WDM network is feasible.

A novel structure of multiwavelength fiber ring laser is proposed, which utilizes erbium-doped fiber cooled by liquid nitrogen and all-fiber M-Z interferometer. The simultaneous oscillation of seven wavelengths with spacing of 0.65 nm was obtained.

In the weakly guiding analysis of cutoff frequencies of elliptical waveguides, the advantages of the proposed elliptical Fourier series expansion method including generality, accuracy, efficiency and simplicity are demonstrated through detailed comparisons with the rigorous Mathieu function method, the finite element method, various important techniques and Dyott′s meansurement on practicle fibers.

Considering the defect of conventional shear interference, it is tested by means of the mathematics and numerical simulation that the shear interference with prolongation wavefront can overcome those drawbacks. The numerical simulation process of wavefront reconstruction with this shear interferometer is given.

An improved 4f Fourier optical system was designed and applied to enlarge the scale of spectrum and realize wavelet transform, which was helpful to the operation of the matched filter on the spectrum plane. The experimental results of Fourier transform and wavelet transform and the fractal dimension on Sierpinski fractal were given.

The interference image spectroscopy coupled with the Doppler effect of electrical and magnetic waves are employed to measure the natural airglow and auroral visible emission lines in the upper atmosphere. The velocity and temperature of the upper atmospheric wind field are analyzed and calculated. The relative velocity of the source to the detector with arbitrary angle to their link line is discussed. Computer simulation is employed for analyzing the effects of the measurement of the upper atmospheric wind field.

A new optic fiber interferometer is proposed for measuring the absolute distance. It consisted of a positioning interferometer and a measuring interferometer, and used the stardard length optic fiber to enlarge the measuring range of the system. The method and the accuracy of the optic path positioning of the system are discussed in detail. Theoretical analysis and experimental results show that the positioning repeatability error is ±1 μm.

The phase measurement error in an interferometric wavelength shift measurement scheme, such as that used in in-fiber Bragg grating sensors, has been investigated experimentally, with appropriate underpinning analytical theory. It has been shown that when a lock-in amplifier is employed to detect the phase shift generated by the Bragg wavelength shift, a pseudo-periodical measurement error can be introduced due to the difference between the amplitude of the optical path difference ramp and value of Bragg wavelength. If the initial ramp deviation equals 20 nm, the measurement error may be as large as 5% of the total measurement range. By using a double-phase lock-in amplifier to measure the AC strain, the measurement error can be decreased to 0.4% of the total measurement range. By using the real-time measured period which corresponds to the Bragg wavelength with the distorted carrier signal of the interferometer as the reference period of a digital lock-in amplifier, the effect of the initial ramp deviation can be principally avoided, and the measurement error can be kept to an acceptably low level, about 0.1% of the total measurement range.

The particle extinction characteristics, determined by receiption in short distance, is discussed. Calculations show that the extinction coefficient in short distance, especially for the large particles, is very different from that in long distance, i.e. it is not only dependent on particle properties, but also the location of particle in measuring beam. Therefore, the above mentioned factors should be taken into account when the short distance receiption is used to measure the particle size. Furthermore, the way to define the measurement volume under the receiption in short distance is also described, the particle diameter and concentration can be clearly determined by above mentioned method.

By using a continuous-wave, LD end-pumped Nd:YAG laser as a model of the experiment, the noises including intensity noise, frequency noise and field distributing noise of the laser are studied. Based on the experiment data, the change of upper energy level life time of Nd:YAG particles on temperature is derived as 1.83 μs/K, and the change of emission section on temperature is -0.146×10-19cm2/K.

Three kinds of pumping schemes are considered for erbium-doped fiber amplifiers (EDFA) pumped in the 980 nm absorption band excluding the effects of ASE process. Based on rate equations and light propagation equations under the condition of the steady-state, implicit and analytical solutions of the pump power and the gain for EDFA have been derived. Using these deduced expressions and numerical simulations, curves of the pump power and the gain as a function of fiber coordinate for different pump powers with small and large input signal, respectively, have been analyzed and discussed in three different pumping configurations, namely, forward pumping, backward pumping and bi-directional pumping.

The mode characteristcs for vertical-cavity surface-emitting lasers (VCSEL) with different cap layer thickness are numerically analyzed. The results show that the threshold gain can increase several times for VCSEL with unmatched cap layer, which results from an anti-phase reflectivity from the air-interface. The mode field intensity distribution inversely increases near the air interface as the reflectivity of the air interface is anti-phase with that of distributed Bragg reflector. A precision etching of the cap layer can be used for improving the laser performance.

The mode matching in high-power end-pumped Nd:YVO4solid-state lasers has been investigated by employing two different Nd3+-doped crystals at pump power of 10 W and 14 W, respectively. The results show that the output power in TEM00mode is insensitive to the ratio of fundamental mode radius to averaged pump spot radius (w1/wpa) over a large range of w1/wpa1/wparatio at which the output power is maximized. The results also indicate that high efficient radiation in single TEM00mode is still available in the situation of very small w1/wparatio due to the aperture effect arising from thermal lens spherical aberrations.

The laser-induced damage of several kinds of dielectric thin-film materials in λ/2 thin-films forms, AR and HR coatings has been studied. The damage threshold has been measured by the 1064 nm laser with single shot and 10 Hz pulse multishot respectively. The data and damage morphologies are discussed in details and some conclusion are drawn concerning pulsed laser-induced damage of the coatings:a) optical materials Er2O3,Y2O3,Gd2O3etc. have high damage threshold with 1064 nm laser at single shot and multishot, specially to 10 Hz laser irradiation, the damage size is smaller than other materials.b) the λ/2 layer SiO2of AR and HR coating has no influence on the onset threshold, but can obviously drop the possibility and level of the damage.

An aluminium diffuser was developed by grinding the aluminium plates with free abrasive, and using a vacuum-deposited layer of pure aluminium. The instruments used for bidirectional reflectance distribution function (BRDF) measurements were established. The BRDF and hemispherical reflectance of the aluminium diffuser was measured. The total hemispherical reflectance of the aluminium diffusing plate is 49% at 315 nm. At normal incidence, the BRDF of the ground aluminium changes about 11% over 15°～40° scattering angle range.

The phase-matching curve of GCOB crystal was calculated and experimentally measured. The measured data of phase-matching angle are well fit to the calculated curve. The second-harmonic generation conversion efficiency of a Q-switched Nd:YAG laser with a GCOB crystal of 5 mm in length is about 26.7%. Comparing its conversion efficiency with that of the same length BBO crystal, the effective nonlinear coefficient is estimated to be close to that of BBO crystal.

The self-pulsation behavior of the phase-conjugated light is studied experimentally in a semilinear self-pumped phase conjugator, which contains two BaTiO3 crystals (one of them operates in total-internal-reflection self-pumped phase conjugator and is used as retro-reflector in this semilinear self-pumped phase conjugator). The frequency f of the pulsation is related to the incident power I0by f∝I01.43. The lasting time of the phase-conjugated light is found to be approximately inversely proportional to I0. The dynamic spatial structure of fanning light is observed and which is responsible for the pulsation of the phase-conjugated light in the semilinear self-pumped phase conjugator.

A more comprehensive theoretical model to deal with the pulsed beam through grating pair is obtained and used to study the spatial and temporal properties of the pulsed Gaussian beam single and double passing compressor and the effects of high-order dispersion. It is found that when the uncollimated input beam single passes through compressor, the time-dependent spatial shift will be introduced in the output pulse, and the duration of the output pulse will depends on the position of the beam waist. In addition, Furthermore, for the single-passed compressor, the third-order dispersion causes the pulse front distortion, and the fourth-order dispersion leads to the time-depended spatial shift in the output pulse.

Intensity space distribution near image point of optical system is derived based on the accurate amplitude (therefore the intensity) analytic expression for Fresnel diffraction. In contrast to Lommel functions, the intensity space distributions are calculated accurately with conventional Baessel function, so it is convenient to be used and the results are perceived more directly. The concept of Fresnel number is also discussed.

A refracting-reflecting flat CCD camera with quick F-ratio and wide field is introduced. The design idea and method are presented. The detailed structure parameters and spot spread diameters are given. The camera covers waveband of 390～900 nm and is divided into blue and red channels in 660 nm. Each channel has a 1024×2048 CCD detector. The camera has excellent image quality with F0.9, diagonal field 22.2°.

According to the responsivity of photoelectric device for a light source, the formula of spectral matching factor of photocathode for object is deduced. The spectral matching factors of S25photocathodes for dark green paint and green vegetation are calculated and compared. To S251, the spectral matching factors for dark green paint and green vegetation are 0.5512 and 0.2783 under the full moon radiation. They are 0.2662 and 0.1255 under the clear star radiation. To S252, the former are 0.7174 and 0.6820 and the latter are 0.5741 and 0.4840. It is referential to evaluate visual range of night vision system through analyzing the results.

The coupled wave equation of two-dimensional Acousto-electro-optical (AEO) effect is derived according to the opinion about interaction of the parameters. A diffraction efficiency formula of the two-dimensional AEO effect is given by the equation.

The probability distribution function of path length of scattering photons in bio-tissue and its statistical properties were studied. Scattering light temporal autocorrelation function was obtained and its decay was discussed.

By using a “Depthometer with an isotropic fiber-optic probe” developed by the authors, the diffuse reflectance as well as the fluence rate distributions in the normal and cancerous human lung tissues irradiated by a collimated broad beam of a violet Kr+laser(406.7～415.4 nm) have been accurately measured. In combination with the diffusion theory and the Adding-Doubling technique, the optical characteristics of human lung tissues, such as the absorption and the reduced scattering coefficients, the penetration depth and the effective attenuation coefficient, were derived. The experimental data agree well with the fitting results by Monte Carlo simulations. It is believed that this original set of data on the optical parameters will be very useful for the lung cancer photodynamic diagnosis (PDD) and the light dosage designations.

The effects of the sampling aperture sizes on the phase conjugation correcting atmospheric turbulence along a horizontal path of 1000 m and 4 m above ground are reported. The results show that the corrected effects and peak energies are related to the sampling aperture sizes, and there is an optimum sampling aperture for a given system.